Method of determining the thickness of a layer on a silicon substrate

Abstract

A method of determining the thickness of a layer on a substrate where the layer is deposited during a semiconductor manufacturing process. The substrate is weighed a first time. The layer is deposited on the substrate and the substrate is weighed a second time. The thickness of the layer is calculated using the difference between the second weighing and the first weighing.

We claim:  
     
       1. In a semiconductor manufacturing process, a method of determining the thickness of a layer on a silicon substrate, the layer having a certain density and the layer being deposited on a certain surface area of the substrate, the method comprising: 
       transferring the substrate from a shipping tray to a weighing device;  
       determining the mass of the substrate by weighing the substrate by the weighing device;  
       transferring the substrate from the weighing device to a reactor tray;  
       depositing the layer on the substrate;  
       transferring the substrate from the reactor tray to the weighing device;  
       determining the combined mass of the substrate and layer by weighing the substrate by the weighing device;  
       determining the mass of the layer from the difference between the combined mass of the substrate and layer, and the mass of the substrate; and  
       calculating the thickness of the layer from the mass of the layer, the surface area of the substrate, and the density of the layer.  
     
     
       2. The method of claim  1 , wherein the calculating step uses the formula          t   =         m   2     -     m   1         A                 ρ         ,                   
       where t is the thickness of the layer, m 2  is the mass of the substrate and the layer, m 1  is the mass of the substrate, A is the area of the substrate upon which the layer is deposited, and ρ is the density of the layer. 
     
     
       3. The method of claim  1 , wherein the depositing step is performed at least partially by epitaxial deposition. 
     
     
       4. The method of claim  1 , wherein the depositing step is performed at least partially by chemical vapor deposition. 
     
     
       5. The method of claim  1  wherein at least one of the limitations of transferring is accomplished by robotically moving the substrate. 
     
     
       6. In a semiconductor manufacturing process, a method of determining the thickness of a plurality of layers on a silicon substrate, each of the plurality of layers having a certain density and the layers being deposited on a certain surface area of the substrate, the method comprising: 
       (a) determining the mass of the substrate prior to the deposition of the plurality of the layers thereon;  
       (b) transferring the substrate from a shipping tray to a reactor tray;  
       (c) depositing a layer on the substrate;  
       (d) determining the combined mass of the substrate and layer by weighing the substrate by a weighing device;  
       (e) determining the mass of the layer from the difference between the combined mass of the substrate and layer, and the mass of the substrate;  
       (f) calculating the thickness of the layer from the mass of the layer, the surface area of the substrate upon which the layer is deposited, and the density of the layer, and  
       (g) repeating steps, (c), (d), (e) and (f) for each of the plurality of layers, the mass of the substrate being defined as the combined mass of the substrate and any layers previously deposited thereon, and the surface area of the substrate being defined as the surface area over which the layer is deposited.  
     
     
       7. The method of claim  6 , wherein the limitation of determining the combined mass of the substrate and layer is accomplished by robotically moving the substrate and layer to the weighing device.